The present invention relates generally to a geospatial database access and query method, and more particularly to a map and Global Positioning System (GPS) navigation process. With the location information provided by a GPS receiver, the geospatial database operations, such as database access and query, are speeded up. With the map data from a geospatial database, the navigation performance and accuracy are enhanced.
A geospatial database has a big volume of spatial and text data which are organized in a file system or in tabular fashion. The data is used by the user to query spatial information and associated features and text descriptions. Due to the amount of a geospatial database, there exists difficulty to efficiently perform database access and query.
The coordinate information is the basic element of a geospatial database. There is a need to incorporate coordinate information into the geospatial database access and query operations.
The Global Positioning System (GPS) is an all-weather, space based navigation system under development by the Department of Defense (DoD) to satisfy the requirements for the military forces to accurately determine their position, velocity, and time in a common reference system, anywhere on the Earth on a continuous basis. To provide a continuous global positioning capability, a scheme to orbit a sufficient number of GPS satellites to ensure that four were always electronically visible was developed. The GPS receiver is used to measure the distances to the satellites. Then the location expressed as latitude, longitude and elevation are derived.
The global positioning system receiver, which includes an antenna, a signal processing unit, and associated electronics, receives signals from the global positioning system satellites to obtain position, velocity, and time solution. The global positioning system principle of operation is based on range triangulation. Because the satellite position is known accurately via ephemeris data, the user can track the satellite""s transmitted signal and determine the signal propagation time. Since the signal travels at the speed of light, the user can calculate the geometrical range to the satellite. The actual range measurement (called the pseudorange) contains errors, for example, bias in the user""s clock relative to global positioning system reference time. Because atomic clocks are utilized in the satellites, their errors are much smaller in magnitude than the users"" clocks. Thus, for three-dimensional position determination, and also to calculate the cock bias, the pure global positioning system needs a minimum of four satellites to obtain the user""s location.
The position accuracy provided by a GPS receiver is roughly 100 meters when only Coarse/Acquisition (C/A) code is employed and the Selective Availability (SA) is on. For personal navigation this position accuracy need to be enhanced. To obtain enhanced navigation function and accuracy, other navigation data should be incorporated in the navigation process, such as a geospatial database.
The main objective of the present invention is to provide an enhanced navigation process, which incorporates the GPS position data and geospatial map data.
Another objective of the present invention is to provide an efficient geospatial database query and access method by using GPS position data in the geospatial data retrieval procedure.
Another objective of the present invention is to provide a time-space filtering method to fully fuse the GPS position data and the geospatial map data to obtain enhanced navigation performance.